Based on my knowledge, and I am by no means an expert, that sounds about right maybe a little on the small side but nothing to really worry about. Every dog is different. Titan is larger than breed standard and never weighed what was "average." I would say as long as she is healthy, eating well, drinking water, energy level is high, and her stools are normal then you are just fine! It also may help us if you post pictures of her from the side and the top.
Commander Charly Titan (GSD)-15 Jan 2010
Lady Athena (BB)-2011-2012 (RIP baby girl)